Unfortunately, the values of resistor we calculated for the RIAA accuracy are not working in the way we expected. The RIAA needs some fine tuning. This will be investigated this week and I'll make an amendment to BOM as soon as we have the level of accuracy I expect.

I have slowly gone about getting the parts for this board. I managed to pick up some Panasonic PP 4.7uF 450VDC caps for C131.231 from RS Components. They fit perfectly into the space allowed. You mention that by doubling up on the 2.2uF you seemed to get better body, so I might try these out too for C132.232 & 144.